Hot-cathode indicator tube for displaying luminescent figures

ABSTRACT

An indicator tube having an anode structure and a hot cathode placed in front of the structure. The structure comprises a base plate and a plurality of phosphor anode segments which are capable of displaying at least one numeric, alphabetic, or similar figure. The tube dispenses with the conventionally required mask by embedding the anode segments within the base plate.

United States Patent Akahane et a].

[451 Sept. 16, 1975 HOT-CATHODE INDICATOR TUBE FOR DISPLAYING LUNIINESCENT FIGURES Inventors: Fumitake Akahane; Tsunekiyo Iwakawa; Hideyo Imai; I-Iiroshi Okazaki; Toshio Wada, all of Tokyo, Japan Assignee: Nippon Electric Company Limited,

Nishishinba, Japan Filed: Feb. 12, 1974 Appl. No.: 441,812

Related U.S. Application Data Continuation of Ser. No. 309,354, Nov. 24, 1972, abandoned, which is a continuation of Set. No. 122,052, March 8, 1971, abandoned.

U.S. CI 313/496; 313/355 Int. Cl. H01J 63/02 Field of Search 313/496, 355, 497, 517

References Cited UNITED STATES PATENTS Bernstein 313/496 3,201,634 8/1965 Weidel et a1 313/497 3,418,509 12/1968 Frouws et a1. 313/496 X 3,508,101 4/1970 Tanji 313/497 3,619,694 1 H1971 Tanji 313/497 Primary Examiner-Palmer C. Demeo Attorney, Agent, or FirmJohn M. Calimafde; Robert A. Schroeder; Stephen B. Judlowe [5 7] ABSTRACT An indicator tube having an anode structure and a hot cathode placed in front of the structure. The structure comprises a base plate and a plurality of phosphor anode segments which are capable of displaying at least one numeric, alphabetic, or similar figure. The tube dispenses with the conventionally required mask by embedding the anode segments within the base plate.

3 Claims, 4 Drawing Figures PATENTEDSEP16|975 3,906,286

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INVENTORS HOT-CATHODE INDICATOR TUBE FOR DISPLAYING LUMINESCENT FIGURES This is a continuation of application Ser. No. 309,354, filed Nov. 24, 1972, which is in turn a continuation of application Ser. No. 122,052, filed Mar. 8, 1971 both of which are now abandoned.

This invention relates to a hot-cathode indicator tube for displaying various, numeric, alphabetic, or similar figures.

A tube of the type mentioned above is described in Electronics, May 29, 1967 issue, pp. 212-213, wherein a hot cathode of a low-enough temperature is disposed in front of an anode structure having a ceramic base plate and a plurality of phosphor anode segments capable of representing a set of numerals and the like. Each anode segment may comprise an electric conductor film and a phosphor film. Lead wires extend from the respective conductor films. A flood electron beam is directed towards the anode segments with substantially uniform density thereon. Only those anode segments to which anode potential is supplied through the pertinent lead wires emit luminescence to display a selected numeral. The luminescence emitted from the edges of the phosphor segments, however, is scattered to result in the dimming of the edges of the indication. Thus, it has heretofore been necessary to provide a mask in front of the anode display to give a clear-cut display.

It is therefore an object of the invention to provide a hot-cathode phosphor indicator tube capable of giving a clear-cut display without using a mask.

According to the invention there is a phosphor indicator tube for displaying at least one luminescent figure at a time, comprising an anode structure having a base plate provided with at least one set of phosphor anode segments, means placed in front of said segments for emitting thermal electrons, means for distributing said electrons substantially uniformly on said segments, and means for supplying a positive potential selectively to said segments, each said set of segments conforming in geometric configuration to a set of figures to be displayed, whereby that segment of each said segment set to which said potential is supplied serves to display said luminescent figure selected out of said set of figures, wherein the improvement comprises no mask conventionally required to give a clear-cut display of said luminescent figure.

According to a preferred aspect of the invention, the base plate is formed of an electric insulating material and provided with at least one set of grooves formed therein, each set of the grooves conforming exactly in geometric configuration to a set of figures to be displayed. The anode segments are placed in the grooves, respectively. The anode segments comprise electric conductor films placed on the bottom walls of the grooves, respectively, in electric contact with the positive potential supplying means and phosphor films placed in the grooves on the conductor films, respectively. The positive potential supplying means comprises lead wires extended from the conductor films, respectively, passing through the base plate. Most preferably, the exposed surfaces of the phosphor films are substantially flush with the front surface of the base plate.

A tube according to the preferred aspect gives a clear-cut display without using the mask, because the phosphor is precisely shaped by the grooves and because the phosphor does not protrude from the front surface of the base plate.

To the accomplishment of the above and to such further objects as may hereinafter appear, the present invention relates to a hot-cathode indicator tube for displaying luminescent figures substantially as defined in the appended claims and as described in the following specification taken together with the accompanying drawing in which:

FIG. 1 is an exploded perspective view showing the inner structure of a conventional hot-cathode phosphor indicator tube for displaying a numeral at a time selected out of the numerals;

FIG. 2 is a section of a part of the anode structure shown in FIG. 1;

FIG. 3 shows a perspective view, with a part cut away, of the anode structure according to this invention; and 1 FIG. 4 is a sectional view of a part of the anode structure shown in FIG. 3.

Referring to FIGS. 1 and 2, a conventional hotcathode phosphor indicator tube comprises an oxidecoated cathode 10, an anode structure or assembly 11 disposed behind the hot cathode l0, and a mask 12 within a vacuum envelope (not shown). Although illustrated apart from the structure 11, the mask 12 is located in close adjacency to the front surface of the structure 11 in fact. The anode structure 1 1 comprises a plurality of phosphor anode segments 13 formed on the front surface of a ceramic base plate 14 in such a manner that the segments 13 may represent any desired numeral. Each segment 13 comprises a conductor film 15 and a phosphor film 16 deposited successively on the base plate 14 and a lead wire extending from the conductor film 15 through the base plate 14. The mask 12 is provided with a plurality of perforations cut to the full depth of the mask 12. The mask 12 serves to precisely and sharply define the outline of the luminous display which would otherwise dim or diffuse in appearance.

Referring to FIGS. 3 and 4, an embodiment of the invention is of a similar construction as the conventional tube illustrated with reference to FIGS. 1 and 2. According to the invention, an anode structure or assembly 18 comprises a base plate 19 formed of ceramics, glass, plastics, or the like in which a plurality of phosphor anode segments 20, similar to the segments 13 shown in FIGS. 1 and 2, are embedded. Each segment 20 is placed in a correspondingly shaped groove or depression 21 formed in the front surface portion of the base plate 19 and comprises an electric conductor film or layer 22 deposited on the bottom wall of the groove 21 and a phosphor film or layer 23 filling the rest of the groove 21. Lead wires 17 are extended from the respective conductor films 22 through the base plate 19.

For example, a soda glass base plate 19 having a thickness of about 0.8 mm and the preliminarily formed through holes for the lead wires 17 is photoetched with ammonium fluoride to form grooves 21 of about 30 microns in depth. The base plate 19 may be shaped of a plastic plate together with the grooves 21 and the through holes. The lead wires 17 are put through the respective holes and secured to the base plate 19 with low melting-point glass. One end of each lead wire 17 should appear in the groove 21 and may even extend a little beyond the front surface of the base plate 19. Metal films 22 of several microns in thickness are formed by the Mesa" coating technique. Alternatively, the conductor films 22 may be deposited by vacuum evaporation of metal or spraying or brashing of graphite. Phosphor is sedimented onto the respective conductor films 22 to result in the phosphor films 23 of the thickness of about microns. Preferably, the phosphor should be applied to the base plate 19 in a little excess and then scraped with a straight edge to leave exposed surfaces of the phosphor films 23 substantially flush with the front surface of the base plate 19.

The figure-of-eight configuration or pattern shown in FIGS. 1 and 3 can display any one of the numerals when pertinent ones of the anode segments 13 or 20 are supplied with the positive potential through the lead wires 17 attached to such segments. The configuration of the segments 13 or 20 may be a plurality of figure-of-eight patterns to display a plurality of digits at a time. The configuration may be otherwise modified to display numerals of a different design or alphabet or other similar figures.

According to the invention, the luminescence emitted from some or all of the phosphor anode segments 20 does not scatter apart but proceeds in a restricted direction because the phosphor films 23 do not protrude from the front surface of the base plate 19. This results in a clear-cut display without the conventionally required mask 12.

Thus, while only a single embodiment of the present invention has been herein specifically described, it will be apparent that modifications may be made therein without departing from the spirit and the scope of the invention.

We claim:

1. In a phosphor indicator tube for displaying at least one luminescent figure at a time, said tube comprising an evacuated sealed envelope, an anode structure within said envelope and having a base plate formed of an insulating material and provided with a plurality of phosphor anode segments, means placed in front of said segments for emitting thermal electrons, means for supplying a positive potential selectively to said anode segments, and means for distributing, in cooperation with the anode segments supplied with said positive potential, said electrons substantially uniformly on said anode segments, the improvement which comprises: at least one set of grooves formed in said base plate, each said set of grooves conforming in geometric configuration and dimension to a set of figures to be displayed, said anode segments each comprising an electroconductive film respectively deposited on the entire surface of the bottom wall of said set of grooves in electric contact with said positive potential supplying means, and a phosphor film respectively filling said grooves over said electroconductive film, and having a peripheral end extending along the periphery of said grooves from said electroconductive film substantially to the front surface of said base plate, whereby those segments in said groove set to which said positive potential is supplied serve to clearly and distinctly display said luminescent figure selected from said set of figures without the use of an additional mask or electrode located between said electron distributing means and said anode structure.

2. A phosphor indicator tube as recited in claim 1, wherein said electron emitting means is an oxidecoated filament.

3. A phosphor indicator tube as recited in claim 1, wherein said potential supplying means comprises lead wires extended from said segments, respectively, passing through said base plate. 

1. In a phosphor indicator tube for displaying at least one luminescent figure at a time, said tube comprising an evacuated sealed envelope, an anode structure within said envelope and having a base plate formed of an insulating material and provided with a plurality of phosphor anode segments, means placed in front of said segments for emitting thermal electrons, means for supplying a positive potential selectively to said anode segments, and means for distributing, in cooperation with the anode segments supplied with said positive potential, said electrons substantially uniformly on said anode segments, the improvement which comprises: at least one set of grooves formed in said base plate, each said set of grooves conforming in geometric configuration and dimension to a set of figures to be displayed, said anode segments each comprising an electroconductive film respectively deposited on the entire surface of the bottom wall of said set of grooves in electric contact with said positive potential supplying means, and a phosphor film respectively filling said grooves over said electroconductive film, and having a peripheral end extending along the periphery of said grooves from said electroconductive film substantially to the front surface of said base plate, whereby those segments in said groove set to which said positive potential is supplied serve to clearly and distinctly display said luminescent figure selected from said set of figures without the use of an additional mask or electrode located between said electron distributing means and said anode structure.
 2. A phosphor indicator tube as recited in claim 1, wherein said electron emitting means is an oxide-coated filament.
 3. A phosphor indicator tube as recited in claim 1, wherein said potential supplying means comprises lead wires extended from said segments, respectively, passing through said base plate. 